Projecting optical unit and projecting type image display apparatus therewith

ABSTRACT

A projection image display device is disclosed in which a trapezoidal distortion and/or aberration are restrained when an image is enlarged and projected obliquely onto a screen. An image generator is connected to an optical system base in such a manner that at least an inclination thereof (on an axis parallel to X axis) with respect to a vertical line and a distance thereof in forward and backward direction (Z axis direction) can be adjusted by an adjusting mechanism. Further, a projecting lens  2  as a first optical system and a free-form curved surface mirror as a second optical system are fixed to the optical system base. The free-form curved surface mirror is rotatable (on an rotary axis parallel to X axis) with respect to the vertical line at a substantial center of the free-form curved surface mirror.

INCORPORATION BY REFERENCE

The present application claims priority from Japanese application JP2005-111516 filed on Apr. 8, 2005, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to a projecting type image displayapparatus for projecting an enlarged multicolor image onto a screen,particularly, a projecting type image display apparatus in which theimage is projected obliquely to the screen so that the enlarged image isformed on the screen, and a projecting optical unit usable for thedevice.

In a projecting type image display apparatus for projecting onto ascreen an image formed by a display element including a reflection ortransmission type liquid crystal panel or micro-mirrors while beingenlarged, a sufficiently enlarged image on the screen as well as areduction of depth length are required. For these requirements, aprojecting optical unit for projecting the image obliquely to the screen(hereafter, called as oblique projection) while enlarging it asdisclosed by JP-A-2001-264627, is known. Further, an optical adjustmentfor a case in which a curved mirror is used for the oblique projection,is disclosed by JP-A-2002-350774.

BRIEF SUMMARY OF THE INVENTION

In the oblique projection in which the image is projected (for example,from a lower area of the screen) with a predetermined angle with respectto a normal line of a main screen plane, the image projected on thescreen includes a trapezoidal distortion and aberration caused by adifference in projecting length between upper and lower portions of thescreen. For solving these, in the above mentioned JP-A-2001-264627, thetrapezoidal distortion is compensated by a free-form curved mirrorarranged between a projecting optical system and the screen and having anegative power. On the other hand, the aberration is compensated by thatan image forming element is moved parallel with respect to a coaxialprojecting optical system or the image forming element is inclined withrespect to the coaxial projecting optical system while being movedparallel with respect to the coaxial projecting optical system.

However, by this compensation of the aberration, there is a provabilityof that the image is shifted vertically on the screen, so that acompensating mechanism therefore is required. Further, when using thecoaxial projecting optical system, an angle of projecting field needs tobe significantly great so that a number of lenses and an aperturethereof are increased.

In the above mentioned JP-A-2002-350774, an adjusting method using themovement of the free-form curved mirror is disclosed, but thecompensation of the aberration is not considered.

As mentioned above, since the trapezoidal distortion and the aberrationare compensated by respective means in the prior art, the diameters andnumber of the lenses need to be great. Therefore, in the above mentionedprior art, decreasing in the oblique projection the depth length and/ora height of a lower portion of the screen while reducing sufficientlythe trapezoidal distortion and aberration (hereafter, called as aset-compacting) is difficult.

The present invention is for solving the above mentioned problems, andan object thereof is to provide a technique preferable for theset-compacting with displaying the image of the reduced trapezoidaldistortion and aberration.

Further, the present invention provides a technique making a productionor assembling adjustment of the compacted set with the above mentioneddisplaying characteristics easy in a rear projection type image displaydevice.

The present invention for the oblique projection is characterized inthat a first optical system having projecting lenses including at leastone asymmetry lens of rotationally asymmetry shape with respect to anoptical axis and of concave light transit surface and a second opticalsystem having a convex mirror having a reflection surface at least apart of which is a convex light reflection surface are fixedly mountedon a common optical system supporting unit.

The asymmetry lens is a free-form curved surface in which a curvature ofa part through which a light beam toward a lower end of a screen passesis greater than a curvature of a part through which a light beam towardan upper end of the screen passes. Further, on the convex mirror, acurvature of a part by which a light beam toward a lower area of thescreen is reflected is greater than a curvature of a part by which alight beam toward an upper area of the screen is reflected, oralternatively, the part by which the light beam toward the lower area ofthe screen is reflected has a convex shape while the part by which thelight beam toward the upper area of the screen is reflected has aconcave shape.

Further, at least one of a mechanism for at least one of an angularadjustment between the optical axis of the projecting lens and adirection in which the light beam is emitted from an image generatorincluding an image display element and an adjustment of optical distancebetween the image generator and the projecting lens, a mechanism forrotational adjustment of the free-form curved mirror on an axis at asubstantially center position of the free-form curved mirror and amechanism for a positional adjustment of a lens group of the greatestpositive power in the projecting lens along the optical axis of theprojecting lens, is included by the present invention.

By the above mentioned structure of the present invention, an image inwhich the trapezoidal distortion and/or aberration caused by the obliqueprojection of the image is reduced is obtainable, and the set-compactingis performed.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross sectional view showing an embodiment of an imagedisplay device of the invention.

FIG. 2 is a cross sectional view showing a basis structure of aprojecting optical unit of the invention.

FIG. 3 is an Y-Z cross sectional view showing the structure and opticalpath of the embodiment of the invention.

FIG. 4 is an X-Z cross sectional view showing the structure and opticalpath of the embodiment of the invention.

FIG. 5 is a view showing a distortion characteristic of the embodimentof the invention.

FIG. 6 is a view showing a spot performance of the embodiment of theinvention.

FIG. 7 is a view showing an embodiment of a projecting optical unit ofthe invention.

FIG. 8 is a view showing an adjusting mechanism of the projectingoptical unit of the invention.

FIG. 9 is a view showing another adjusting mechanism of the projectingoptical unit of the invention.

FIG. 10 is a cross sectional view of the projecting optical unit of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Hereafter, an embodiment of the invention will be explained with makingreference to the drawings.

FIG. 1 is an oblique projection partially cross sectional view of animage display device of the invention. An image generator 1 displays animage of small size. The image generator 1 includes a reflection ortransmission type liquid crystal panel or an optical modulating elementsuch as a display element including micro-mirrors. Further, the imagegenerator 1 may include a projection type braun tube. An image of theimage generator 1 is projected onto a screen 3 through a projecting lens2 as a component of a first optical system. A planar reflection mirror 4is arranged on an optical path from the projecting lens 2 to the screen3 to decrease a depth length of the image display device. A free-formcurved mirror 5 as a component of a second optical system is arrangedbetween the projecting lens 2 and the planar reflection mirror 4. Alight from the projecting lens is reflected by the free-form curvedmirror 5 to be guided onto the planar reflection mirror 4, and reflectedby the planar reflection mirror 4 to be guided onto the screen 3. Thesemembers are contained by an inside of a frame 6 and fixed to respectivepredetermined positions. Further, the image generator 1, projecting lens2 and free-form curved mirror 5 are fixed to an optical system base 7.Hereafter, a distinctive feature of the components of the projectingoptical unit of the invention will be explained with making reference tothe drawings.

FIG. 2 is a cross sectional view showing a basic optical structure of arear projection type image display device in which the projectionoptical unit of the embodiment is used. FIG. 2 shows the structure ofthe optical system on a Y-Z cross section in XYS orthogonal coordinatessystem. Here, an origin point of the XYS orthogonal coordinates systemis at a center of an image display surface of an image display element11 of the image generator 1, and Z coordinate axis is parallel to anormal line of the screen 3. Y coordinate axis is parallel to a shortside edge of the screen and a horizontal direction of the screen. Xcoordinate axis is parallel to a long side edge of the screen and avertical direction of the screen.

As shown in FIG. 2, the light emitted from the image display element 11passes through a front group 12 of dioptric lenses having respectiverotationally symmetrical surfaces shapes in the projecting lens 2 as thetransmission type lens group, and thereafter passes through a rear group13 including a lens (hereafter, called as a free-form curved surfacelens) in the projecting lens, at least one surface (at least one of sidesurfaces of the lens opposite to each other in a direction parallel tothe light) of which lens has a rotationally asymmetrical free-formcurved surface shape. Thereafter, the light is reflected by at least onereflection mirror (hereafter, called as a free-form curved surfacemirror) having a rotationally asymmetrical free-form curved reflectingsurface, subsequently reflected by the planar reflection mirror 4, andfinally reaches the screen 3.

When the image display element 11 is the optical modulating element, anilluminating system such as a lamp or the like for illuminating theoptical modulating element is needed, however, such system is not shownin the drawings. Further, the image display element 11 may be a typesuch as a so-called three-plates type in which a plurality of the imagesare combined. A combining optical system such as a prism for suchcombination is also not shown in the drawings.

Since a length of the projecting lens 2 is long in FIG. 2, a distancebetween the image display element 11 and the screen in a direction ofthe normal line of the screen seems to be great so that the depth isincreased. However, in the embodiment, a mirror (not shown) is arrangedbetween the free-form curved surface mirror 5 and the rear group 13 ofthe projecting lens 2, between the front and rear groups 12 and 13 ofthe projecting lens 2 or in an intermediate position in the front group12. Therefore, the optical axis of the projecting lens 2 is bent to adirection perpendicular to the cross section of FIG. 2 so that theincrease of the depth is prevented.

In the embodiment, as shown in FIG. 2, the image display element 11 isarranged in such a manner that a center of the display surface isarranged on the optical axis of the projecting lens 2. Therefore, thelight beam 21 emitted from the center of the display surface of theimage display element 11 and passing through a center of entrance pupilof the projecting lens toward a center of an image plane on the screen21 proceeds substantially along the optical axis of the projecting lens2 (hereafter, called as an image center light beam). After beingreflected at a point P2 on the reflecting surface of the free-formcurved surface mirror 5, the image center light beam is reflected at apoint P5 on the planar reflection mirror 4, and reaches a point P8 at acenter of the image plane on the screen 3 with a predetermined anglewith respect to (that is, obliquely to) the normal line 8 of the screen.This angle is called hereafter as an oblique incident angle θs.

In other words, the light beam proceeding along the optical axis of theprojecting lens 2 reaches the screen obliquely to the screen, so thatsubstantially the optical axis of the projecting lens 2 is oblique tothe screen. By the oblique incidence onto the screen in this method,so-called trapezoidal distortion as change in projection fromrectangular shape to trapezoidal shape as well as various aberrationsasymmetrical with respect to the optical axis occur. In this embodiment,these are corrected by the rear group 13 of the projecting lens 2 andthe reflecting surface of the second optical system.

In the cross section shown in FIG. 2, a light beam 22 is emitted from alower end of the image plane of the image display element 11 andproceeds through the center of the entrance pupil of the projectinglens. 2 to the corresponding point P9 at an upper end of the image planeon the screen. Further, a light beam 23 is emitted from an upper end ofthe image plane of the image display element 11 and proceeds through thecenter of the entrance pupil of the projecting lens 2 to thecorresponding point P7 at a lower end of the image plane on the screen.As shown in FIG. 2, an optical path length from the point P3 through thepoint P6 to the point P9 is longer than an optical path length from thepoint P1 through the point P4 to the point P7. This means that as seenfrom the projecting lens 2 toward the screen, the image point P9 isfarther than the image point P7. Therefore, an inclination of the imageplane is corrected by that a distance between an object point (a pointon the image plane) corresponding to the image point P9 on the screenand the projecting lens 2 is relatively decreased and a distance betweenan object point corresponding to the image point P7 and the projectinglens 2 is relatively increased. For this, a normal vector at the centerof the image plane on the image display element 1 is inclined to theoptical axis of the projecting lens 2. Concretely, the normal vector isinclined toward the screen in Y-Z plane. A method for inclining theobject plane to obtain an image plane inclined to the optical axis isknown. However, the image plane formed by inclining the object planeincludes a distortion asymmetrical with respect to the optical axis in apracticable angle of field, so that it cannot be corrected by aprojecting lens symmetrical rotationally. In this embodiment, since thefree-form curved surface which is not rotationally symmetrical but isrotationally asymmetrical is used, the asymmetrical distortion of theimage can be corrected. Therefore, the distortion in low dimension ofthe image plane can be reduced by inclining the object plane so that thecorrection of aberration is effectively assisted by the free-form curvedsurface.

Next, an influence of each optical element is explained. The front group12 of the projecting lens 2 as the first optical system is a main lensfor projecting onto the screen 3 the displayed image on the imagedisplay element 11, and corrects the basis aberration in therotationally symmetrical optical system. The rear group 13 of theprojecting lens 2 includes the free-form curved surface lensasymmetrical rotationally. In the embodiment, the free-form curvedsurface lens is curved to be concave in a light emitting direction. Acurvature of a part of the free-form curved surface lens through whichthe light beam toward the lower end of the screen 3 is made greater thana curvature of a part of the free-form curved surface lens through whichthe light beam toward the upper end of the screen 3. The second opticalsystem includes a free-form curved surface mirror having a free-formcurved surface shape asymmetrical rotationally. In this embodiment, thefree-form curved surface mirror is a convex surface mirror asymmetricalrotationally, a part of which is curved to be convex in a reflectingdirection of the light. Concretely, a curvature of a part of thefree-form curved surface mirror for reflecting the light toward thelower area of the screen is made greater than a curvature of a partthereof for reflecting the light toward the upper area of the screen.The part of the free-form curved surface mirror for reflecting the lighttoward the lower area of the screen may be convex in the reflectingdirection of the light, and the part thereof for reflecting the lighttoward the upper area of the screen may be concave in the reflectingdirection of the light. By the free-form curved surface mirror and thefree-form curved surface lens, the aberration mainly caused by theoblique incidence is corrected. That is, the second optical systemmainly corrects the trapezoidal distortion, and the rear group 13 of theprojecting lens 2 as the first optical system mainly corrects theasymmetrical aberration such as the distortion of the image or the like.

As mentioned above, in the embodiment, the first optical system includesat least one free-form curved surface lens asymmetrical rotationally,and the second optical system includes at least one free-form curvedsurface mirror. Therefore, both of the trapezoidal distortion and theaberration caused by the oblique projection can be corrected.

It is preferable for a distance along the optical axis between theorigin point of the coordinate system of the reflection surface of thesecond optical system (here, a position at which the central light beamof the image is reflected) and a surface of one of the lenses of thefront group 12 of the projecting lens closest to the screen to be notless than 5 times of a focal distance of the front group of theprojecting lens. Therefore, the trapezoidal distortion and theaberration can be effectively corrected by the reflecting surface of thesecond optical system to obtain an improved performance.

On the other hand, since the greater a size of the free-form curvedsurface mirror is, the more difficult a production thereof becomes, itis important for the free-form curved surface mirror to be not greaterthan a predetermined size. For example, since a size of the planarsurface reflection mirror 4 as shown in FIG. 2 is about not less than70% of the image plane on the screen, its size for a great display rearprojector of not less than 50 inches becomes more than 500 mm, so that aproduction thereof with the free-form curved surface shape becomes verydifficult. Therefore, it is not preferable that the planer surfacereflection mirror for the rear projector is replaced by the free-formcurved surface mirror. Accordingly, in the embodiment, a size of thefree-form curved surface mirror 5 is made smaller than a size of theplaner surface reflection mirror 3, and the free-form reflection mirror5 is arranged below the planer surface reflection mirror 3. The imagelight from the projecting lens 2 is reflected by the free-form curvedsurface mirror 5 and subsequently by the planer surface reflectionmirror to be projected onto the screen 3.

The above explanation is based on the embodiment shown in FIG. 2.However, the concept of the above mentioned embodiment is applicable toa case in which a bending direction of the optical path by the mirror isarranged by a plane including the longer side of the image planecontrary to FIG. 2.

Accordingly, in the projecting lens 2 including a refracting surface,the trapezoidal distortion caused by the oblique projection can becorrected without an increase of the number of the lenses. Further, theprojection optical unit of the small depth can be produced easily.Further, in the embodiment, a compact set of the reduced depth andheight under the screen can be provided, and the production of theoptical system can be made easy by the small free-form curved surfacemirror.

Hereafter, the embodiment of the optical system of the invention will beexplained with indicating concrete numerical values as example. Onenumerical example is explained with using fogs. 3-6 and tables 1-4.

FIGS. 3 and 4 are views showing the light beam based on a firstnumerical example. In the above mentioned XYZ orthogonal coordinatesystem, FIG. 3 shows a structure on YZ cross section, and FIG. 4 shows astructure on XZ cross section. In FIG. 1, an example in which a bendingmirror is arranged at the intermediate position of the front group 12 ofthe projecting lens 2 to bend the optical path by one time to the X axisdirection. In FIG. 3, this bending mirror is eliminated, and the opticalsystem is expanded to the Z axis direction. FIG. 4 shows the opticalsystem with the bending mirror in a bent condition. The bending mirrorhas a tolerance in its arranged position and angle, and no effect forperformance of each optical element. Therefore, an explanation of thebending mirror is eliminated in the below explanation.

In this embodiment, the light emitted from the image display element 11shown in a lower side of FIG. 3 passes at first through the front group12 composed of the lenses having the rotationally symmetrical surfacesin the projecting lens 2. Subsequently, it passes through the rear group13 including the free-form curved surface lens asymmetrical rotationallyto be reflected by the reflecting surface of the free-form curvedsurface mirror 5 as the second optical system. The reflected lightproceeds onto the screen 3 after being reflected by the planar surfacereflecting mirror 4.

The front group 12 of the projecting lens 2 is composed of the pluralityof lenses having respective refracting surfaces symmetricalrotationally, four ones of the refracting surfaces are aspherical androtationally symmetrical, and the remainder ones thereof are spherical.The aspherical and rotationally symmetrical surfaces are represented bythe following formula in a local cylindrical coordinate system for eachsurface.

$\begin{matrix}{Z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {( {1 + k} )c^{2}r^{2}}}} + {A \cdot r^{4}} + {B \cdot r^{6}} + {C \cdot r^{8}} + {D \cdot r^{10}} + {E \cdot r^{12}} + {F \cdot r^{14}} + {G \cdot r^{16}} + {H \cdot r^{18}} + {J \cdot r^{20}}}} & \lbrack {{formula}\mspace{14mu} 1} \rbrack\end{matrix}$

A distance from the optical axis is r, and a sag amount is Z. Further, acurvature at a peak is c, a conical constant is k, and coefficients ofsections for power with respect to r are A-J.

The free-form curved surface lens in the rear group 13 of the projectinglens 2 is represented by the following formula including polynomialequations for X and Y in a local orthogonal coordinate system (x, y, z)whose origin point is a surface peak of each surface.

$\begin{matrix}{Z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {( {1 + k} )c^{2}r^{2}}}} + {\sum\limits_{m}{\cdot {\sum\limits_{n}( {{C( {m,n} )} \cdot x^{m} \cdot y^{n}} )}}}}} & \lbrack {{formula}\mspace{14mu} 2} \rbrack\end{matrix}$

A sag amount of the free-form curved surface in a directionperpendicular to X and Y axes is Z, a curvature at the peak is c, adistance from the origin point in the plane of X and Y axes is r, aconical constant is k, and a coefficient for polynomial equation is C(m,n).

Table 1 shows numerical data of the optical system of the embodiment. Intable 1, S0-S23 correspond to reference codes S0-S23 in FIG. 10. S0denotes the display surface of the image display element 11, that is,the object face, and S23 denotes the reflecting surface of the free-formcurved surface mirror 5. S24 not shown in FIG. 10 denotes the incidencesurface of the screen 3, that is, the image face. Incidentally, in FIG.10, an upper part thereof is a vertically cross sectional view of thefirst and second optical systems, and a lower part thereof is ahorizontally cross sectional view thereof.

In table 1, a curvature radius of each surface is Rd, and has a positivevalue when a center of the curvature is at a left side of the surface inFIG. 3 and a negative value when being opposite side. In table 1, TH isa distance between the surfaces, that is, a distance from the peak ofthe surface of one of the lenses to the peak of the surface of theadjacent other one of the lenses. The distance of the one of the lensesbetween the surfaces has a positive value when the surface of theadjacent other one of the lenses is arranged at a left side in FIG. 3,and a negative value when being at a right side. Further, S5, S6, S17and S18 in table 1 are aspherical and rotationally symmetrical, and havesuffixes * attached to the surface denoting codes in table 1 to beeasily recognized. Coefficients of these four aspherical surfaces aresown in table 2.

In table 1, S19-S22 are refraction surfaces of the free-form curvedsurface lens included by the rear group 13 of the projecting lens 2, andS23 is the reflecting surface of the free-form curved surface mirror 5as mentioned above, while the denoting codes for the surfaces havesuffixes #. Table 3 shows values of coefficients representing the shapeof these five free-form curved surfaces.

In this embodiment, the object face as the image display of the imagedisplay element 11 is inclined with respect to the optica axis of theprojecting lens 2 by −1.163 degree. A direction of the inclination has apositive value when a normal line of the object face is rotatedanti-clockwise in the cross section of FIG. 3. Therefore, in theembodiment, the object face is rotated clockwise from a positionperpendicular to the optical axis of the projecting lens by 1.163 degreein the cross section of FIG. 3.

The free-form curved surface mirror 5 as S23 has an origin point of itslocal coordinate on the optical axis of the projecting lens 2. A normalline at the origin point of the local coordinate of the free-form curvedsurface mirror 5, that is, the Z axis, is inclined from a positionparallel to the optical axis of the projecting lens 2 by 29 degrees. Theinclination has a positive value when being rotated anti-clockwise inthe cross section of FIG. 3 similarly to the object face, that is, beinginclined anti-clockwise. Accordingly, the image center light beamemitted from the center of the image on the image display element 11 andproceeding substantially along the optical axis of the projecting lens 2is reflected by S23, and subsequently proceeds in a direction inclinedwith respect to the optical axis of the projecting lens by 58 degrees oftwo times of the inclining angle. New optical axis after being reflectedis along a direction passing the origin point of the coordinate of S23and inclined by two times of the inclining angle of S23 with respect tothe optical axis of the projecting lens 2, and the following surfacesare arranged on this optical axis. The distance value of −400 betweenthe surfaces of S23 on table 1 indicates that the following S24 isarranged at the right side of S23 and the origin point of the localcoordinate of S24 is distant by 400 mm along the optical axis afterbeing reflected. The following surfaces are arranged in the same order.

Table 4 indicates an inclination and eccentricity of the localcoordinate of each surface of the embodiment. In FIG. 4, values of theinclining angle and eccentricity are shown at right sides of the surfacenumbers, ADE is an amount of the inclination in a face parallel to thecross section of FIG. 3, and the indicating order is as mentioned above.YDE is an amount of the eccentricity, the eccentricity is set in adirection perpendicular to the optical axis and in a plane parallel tothe cross section of FIG. 3, and the eccentricity toward the lower sidein the cross section of FIG. 3 has a positive value. Incidentally, YDEis 0 (that is, no eccentricity) in the embodiment.

According to the invention, the inclinations and eccentricities of allof the optical elements are set in the directions on the cross sectionsparallel to the cross sections of the drawings.

From tables 1 and 3, it is known that the curvature c and Korenichconstant k are 0 in the embodiment. The trapezoidal distortion caused bythe oblique projection increases significantly in the direction of theoblique projection, and a distortion amount in a direction perpendicularthereto is small. Therefore, the performance in the direction of theoblique projection and the performance in the direction perpendicularthereto need to be significantly different from each other, and theasymmetrical aberration is sufficiently corrected by preventing thecurvature c and Korenich constant k rotationally symmetrical andeffective for all directions from being used.

TABLE 1 Surface Rd TH nd νd S0 Infinity 10.00 S1 Infinity 31.34 1.5182748.0 S2 Infinity 7.06 S3 246.358 4.65 1.85306 17.2 S4 −84.858 18.00 S5 *−83.708 9.00 1.49245 42.9 S6 * −75.314 0.10 S7 41.651 9.32 1.49811 60.9S8 −42.282 2.50 1.76014 20.0 S9 29.550 0.10 S10 29.476 9.00 1.49811 60.9S11 −79.153 25.90 S12 Infinity 9.10 S13 −265.353 6.00 1.85306 17.2 S14−53.869 65.00 S15 −24.898 4.19 1.74702 33.2 S16 −58.225 9.00 S17 *−27.332 10.00 1.49245 42.9 S18 * −32.424 2.50 S19 # Infinity 8.001.49245 42.9 S20 # Infinity 20.51 S21 # Infinity 8.00 1.49245 42.9 S22 #Infinity 160.99 S23 # Infinity −400.00 REFL S24 Infinity 305.00 REFL S25Infinity —

TABLE 2 Surface Aspheric surface coefficient S5  K −11.7678542 C −1.159E−11 F 2.98642E−20 J  −1.255E−26 A −2.7881E−06 D −3.2834E−14 G1.05201E−21 B 9.67791E−09 E 1.09359E−16 H 1.96001E−24 S6  K −5.4064901 C 2.0324E−12 F  3.0211E−19 J −1.4982E−26 A 6.14967E−07 D −2.2078E−14 G4.30049E−22 B 4.60362E−09 E −8.0538E−17 H 4.79618E−24 S17 K 1.016429122C −9.0262E−11 F −1.0521E−18 J −6.0837E−26 A −1.1068E−05 D −1.3984E−13 G−8.1239E−23 B 7.21301E−08 E  3.1153E−16 H 3.86174E−23 S18 K 0.742867686C −2.2719E−11 F 1.09398E−19 J 9.02232E−29 A 1.51788E−07 D −4.6853E−14 G1.62146E−22 B 2.10472E−08 E  2.9666E−17 H −3.0801E−25

TABLE 3 Surface Free from surface coefficient S19 C(4,1) 5.38933E−07C(2,5) −1.2381E−09 C(4,5) −7.4126E−14 K 0 C(2,3) 8.33432E−07 C(0,7)1.13944E−09 C(2,7) 2.05074E−12 C(2,0) 0.013500584 C(0,5) −4.6367E−08C(8,0) 3.87771E−12 C(0,9) −9.2166E−13 C(0,2) 0.003493312 C(6,0)−6.2643E−09 C(6,2) 1.04779E−11 C(10,0) −2.5867E−15 C(2,1) −0.00083921C(4,2) −2.2449E−08 C(4,4) 1.80038E−11 C(8,2) −8.7122E−15 C(0,3)−0.00032098 C(2,4) −5.6706E−08 C(2,6) 5.23019E−11 C(6,4) 2.85321E−14C(4,0) 8.59459E−06 C(0,6) 9.69952E−10 C(0,8) 1.69253E−11 C(4,6)−8.5084E−14 C(2,2) 2.14814E−06 C(6,1) −1.1968E−10 C(8,1)   −2.7E−14C(2,8) 1.25198E−13 C(0,4) 7.54355E−06 C(4,3) −1.3638E−09 C(6,3)7.30978E−13 C(0,10) −5.6277E−14 S20 C(4,1) 7.49262E−07 C(2,5)−5.7462E−10 C(4,5) −3.6141E−13 K 0 C(2,3) 1.19039E−06 C(0,7) 1.27396E−09C(2,7) 8.54188E−14 C(2,0) 0.015488689 C(0,5) −1.2953E−07 C(8,0)−4.7746E−12 C(0,9) −5.3469E−13 C(0,2) 0.006553414 C(6,0)  5.115E−10C(6,2) 7.32855E−12 C(10,0) 8.92545E−17 C(2,1) −0.00116756 C(4,2)−2.1936E−08 C(4,4) 5.30157E−11 C(8,2) −5.3434E−15 C(0,3) −0.00033579C(2,4) −5.9543E−08 C(2,6) 5.05014E−11 C(6,4) 1.96533E−14 C(4,0) 7.5015E−06 C(0,6) 2.03972E−08 C(0,8) −2.1894E−11 C(4,6) −1.3923E−13C(2,2) −2.5728E−06 C(6,1) 1.16701E−11 C(8,1) −1.2515E−13 C(2,8)1.06322E−13 C(0,4) −1.3543E−06 C(4,3) −1.6198E−09 C(6,3) 7.64489E−13C(0,10) −4.6602E−15 S21 C(4,1) −1.0379E−07 C(2,5) 2.81743E−10 C(4,5)−8.1775E−15 K 0 C(2,3)  3.0082E−08 C(0,7) 6.05663E−10 C(2,7) 3.06022E−14C(2,0) 0.015096874 C(0,5) 7.95521E−08 C(8,0) 8.39381E−13 C(0,9)−9.1775E−13 C(0,2) 0.009982808 C(6,0) −1.3911E−09 C(6,2) 1.98531E−12C(10,0) −7.8543E−17 C(2,1) 0.000358347 C(4,2) 9.33292E−10 C(4,4)1.37477E−11 C(8,2) −8.9588E−16 C(0,3) 0.000209267 C(2,4) 3.54468E−09C(2,6) −1.0671E−11 C(6,4) −6.0768E−15 C(4,0) −3.8593E−07 C(0,6) 4.1615E−09 C(0,8) 9.04109E−12 C(4,6) −1.9528E−14 C(2,2) −6.8336E−06C(6,1) −1.2331E−11 C(8,1) 2.48401E−14 C(2,8)  2.6781E−14 C(0,4) 2.2455E−05 C(4,3) −2.3367E−10 C(6,3) 6.92603E−14 C(0,10) −1.4324E−14S22 C(4,1) −3.6973E−07 C(2,5)  4.8045E−10 C(4,5) −2.9795E−13 K 0 C(2,3)−3.0682E−07 C(0,7) 1.43328E−10 C(2,7) −2.5306E−14 C(2,0) 0.022813527C(0,5) 4.12093E−08 C(8,0) −2.0707E−12 C(0,9) −3.9401E−13 C(0,2)0.012060543 C(6,0) 4.07969E−09 C(6,2) −4.9221E−12 C(10,0) 6.88651E−16C(2,1) 0.000638931 C(4,2)  8.5986E−09 C(4,4) −2.3681E−12 C(8,2)1.55006E−15 C(0,3) 0.000196027 C(2,4)  2.1713E−08 C(2,6) −2.1567E−11C(6,4) −1.4674E−15 C(4,0) −7.1204E−06 C(0,6) 1.63499E−08 C(0,8)−2.3679E−12 C(4,6) −9.9822E−15 C(2,2)  −1.269E−05 C(6,1) 1.38704E−10C(8,1) −5.7167E−15 C(2,8) 2.72925E−14 C(0,4) −2.5184E−05 C(4,3)2.02372E−10 C(6,3) −9.0337E−14 C(0,10) −1.1966E−14 S23 C(4,1)−1.1083E−09 C(2,5) −4.9118E−14 C(4,5) −5.4918E−19 K 0 C(2,3) −5.7768E−10C(0,7) 8.12546E−14 C(2,7) −2.2569E−18 C(2,0) 0.001597194 C(0,5)1.60076E−10 C(8,0)  −7.486E−17 C(0,9) −3.5657E−18 C(0,2) 0.001324181C(6,0) 1.91534E−12 C(6,2) 6.80626E−16 C(10,0) 1.09883E−21 C(2,1)1.37885E−05 C(4,2) −1.0665E−11 C(4,4) −5.1295E−17 C(8,2) −2.1535E−20C(0,3) 1.34349E−05 C(2,4) −8.6063E−12 C(2,6) −3.6526E−16 C(6,4)2.01763E−20 C(4,0) −4.8064E−08 C(0,6) −1.1125E−12 C(0,8) 1.46399E−15C(4,6) −1.2016E−20 C(2,2) 5.24071E−08 C(6,1) 6.24714E−14 C(8,1)−2.1563E−18 C(2,8) 3.21408E−21 C(0,4) 9.53861E−08 C(4,3) −3.4381E−14C(6,3) 2.86073E−18 C(0,10) −1.4922E−19

TABLE 4 Surface ADE (°) YDE(mm) S0 −1.163 0.0 S23 29.000 0.0 S24 −43.0000.0 S25 30.000 0.0

Numerical values in the above tables 1-4 are for a case in which animage of a size 16×9 on the object plane is projected to have a size1452.8×817.2 on the screen. The distortion of the image at this case isshown in FIG. 5. A longitudinal direction of FIG. 5 is a verticaldirection of FIG. 3, that is, the direction of Y axis. A transversedirection of FIG. 5 is a direction perpendicular to the Y axis on thescreen, and a center of the rectangular shape in the drawing is thecenter of the image. A bent condition of a straight line on the imageplane divided longitudinally to four parts and divided transversely toeight parts is shown in the drawing so that the distortion of the imageis shown.

Spot diagrams of the embodiment with the numerical values are shown inFIG. 6. In FIG. 6, spot diagrams of luminous fluxes emitted respectivelyfrom eight points (8, 4.5), (0, 4.5), (4.8, 2.7), (8, 0), (0, 0), (4.8,−2.7), (8, −4.5) and (0, −4.5) in values on X-Y coordinates on the imageplane of the image display element 11 are shown in order from the top.Unit is mm. A transverse direction of each of the spot diagrams is the Xdirection on the screen, and the longitudinal direction thereof is Ydirection on the screen. As stated above, both have good performances.

The optical unit of the embodiment of the invention is explained above.The embodiment is differentiated from the patent document 1 as the priorart by that the rear group 13 of the projecting lens 2 is formed by thefree-form curved surface lens, and the second optical system is formedby the free-form curved surface reflection surface asymmetricalrotationally. Further, roles of these are independent of each other, sothat the second optical system corrects mainly the trapezoidaldistortion, and the rear group 13 of the projecting lens 2 as the firstoptical system corrects mainly the asymmetrical aberration such as thedistortion of the image plane.

Therefore, in the embodiment, the adjustment for focusing during theassembling cannot be brought about by moving a lens group of an imageforming optical system along its axis as the prior art.

FIG. 7 shows the lens group of the projecting lens 2 as the projectingoptical unit of the embodiment, while a lens holder for holding the lensgroup is not shown in the drawing. The front group 12 of the projectinglens 2 is the main lens for projecting onto the screen (not shown) thedisplayed image on the image display element 11, and is composed by theplurality of the dioptric lenses having the rotationally symmetricalsurfaces so that the basis aberration in the rotationally symmetricaloptical system is corrected. The rear group 13 of the projecting lens 2includes the free-form curved surface lens rotationally asymmetrical tomainly correct the aberration caused by the oblique projection.

As apparent from FIG. 7, in the embodiment, at least one of thefree-form curved surface lenses is curved to be concave in the lightemitting direction. Further, the curvature of the part (the lower sideof the free-form curved surface lens) of the free-form curved surfacelens through which the light beam toward the lower end of the screen 3passes is made greater than the curvature of the part (the upper side ofthe free-form curved surface lens) of the free-form curved surface lensthrough which the light beam toward the upper end of the screen 3passes. Further, in the embodiment, the rear group 13 of the projectinglens 2 is a pair of the free-form curved surface lenses.

In the embodiment, the turning mirror 14 is arranged in the intermediateposition of the front group 12. In the prior art, for moving axially thelens group of the image forming optical system, the lens holder (lenstube) has an oblique groove along which the inner lens group is rotatedin the embodiment, since the rotationally asymmetrical free-form curvedsurface lens is used, the rear group 13 including the rotationallyasymmetrical free-form curved surface lens should not be rotated.Therefore, in the embodiment, the lens group cannot be moved along theoptical axis as the above mentioned prior art. On the other hand, sincethe front group 12 of the projecting lens 2 of the embodiment is formedby the rotationally symmetrical lens group, the optical image is notdeformed by the rotation of the front group 12. Therefore, the focusingcan be performed by moving axially the front group 12. However, by thisfocusing, the position of the light beam reaching the incident face ofthe rear group 13 for correcting the aberration changes. By the changeof the position of the light beam, there is a provability of that therear group 13 cannot correct sufficiently the aberration. Therefore, inthe embodiment, a positional relationship between the front and reargroups 12 and 13 of the projecting lens 2 is fixed, and the positionand/or inclination of the image display element 11 beyond the projectinglens is changed for the focusing during the assembling and adjusting.

FIG. 8 shows an embodiment of the optical unit having such adjustingmechanism. In FIG. 8, the image generator 1 has, for example, atransmission type liquid crystal panel of three-plates type, or thereflection type crystal panel. Further, it may have a display elementhaving the micro-mirrors. The projecting lens 2 has the turn mirror 14as shown in FIG. 7 at the intermediate position of the front group 12.The free-form curved surface mirror 5 is connected to the optical systembase 7 integrally together with the image generator 1 and the projectinglens 2. The projecting lens 2 as one of the members connected to theoptical system base 7 is rigidly fixed and united. On the other hand,the image generator 1 is connected to the optical system base 7 in sucha manner that at least its inclination (on a pivotal axis parallel tothe X axis) with respect to a vertical line and its distance in aforward and backward direction (Z axis direction), that is, a distancebetween an outgoing side of the image generator 1 and the front group 12can be adjusted by an adjusting mechanism 15 as the claimed commonoptical system support unit. (That is, the adjusting mechanism 15 has atleast one of a rotary support (for example, rotary bearing) foradjusting the inclination of the image display plane of the imagegenerator 1 with respect to the optical axis of the projecting lens 2and an axial support (for example, a splined linear bearing unit) foradjusting a distance along the optical axis of the projecting lens 2between the image display plane of the image generator 1 and theprojecting lens 2 or the optical system base 7 to which the projectinglens 2 including the rotationally symmetrical lens and rotationallyasymmetrical lens fixed to each other in rotational and axial positionalrelationship therebetween is fixed in rotational and axial positionalrelationship between the projecting lens 2 and the optical system base 7while keeping the rotational positional relationship between the imagedisplay plane of the image generator 1 and the projecting lens 2 or theoptical system base 7 unchanged and/or keeping the rotational and axial(along the optical axis of the projecting lens 2) positionalrelationship between the rotationally symmetrical lens and rotationallyasymmetrical lens unchanged, and a fixing member 15 a (for example, ascrew pressing the image generator 1 against the optical system base 7to be kept stationary with respect to each other or an adhesive adheringto the image generator 1 and optical system base 7 to be kept stationarywith respect to each other) for fixing the inclination of the imagedisplay plane of the image generator 1 with respect to the optical axisof the projecting lens 2 and/or the distance along the optical axis ofthe projecting lens 2 between the image display plane of the imagegenerator 1 and the projecting lens 2 or the optical system base 7 afterthe inclination of the image display plane of the image generator 1 withrespect to the optical axis of the projecting lens 2 and/or the distancealong the optical axis of the projecting lens 2 between the imagedisplay plane of the image generator 1 and the projecting lens 2 or theoptical system base 7 is adjusted. When adjusting the distance along theoptical axis of the projecting lens 2 between the image display plane ofthe image generator 1 and the projecting lens 2 or the optical systembase 7, the adjusting mechanism 15 prevents the relative rotationaland/or axial movement between the rotationally symmetrical lens androtationally asymmetrical lens of the projecting lens 2 so that therotational and/or axial positional relationship between the rotationallysymmetrical lens and rotationally asymmetrical lens of the projectinglens 2 is prevented from being changed by adjusting the distance alongthe optical axis of the projecting lens 2 between the image displayplane of the image generator 1 and the projecting lens 2 or the opticalsystem base 7, and prevents the relative rotational movement between theimage display plane of the image generator 1 and the projecting lens 2or the optical system base 7 so that the rotational positionalrelationship between the image display plane of the image generator 1and the projecting lens 2 including the rotationally symmetrical lensand rotationally asymmetrical lens or the optical system base 7 isprevented from being changed by adjusting the distance along the opticalaxis of the projecting lens 2 between the image display plane of theimage generator 1 and the projecting lens 2 or the optical system base7.) The free-form curved surface mirror 5 is connected through asupporter 16 to the optical system base 7 in such a manner that thefree-form curved surface mirror 5 is rotatable on an axis (pin 17)passing a substantially center of the free-form curved surface mirror 5and fixed to the optical system base 7, and is capable of beingrotationally fixed by the supporter 16 to the optical system base 7after being adjusted in rotational position of the free-form curvedsurface mirror 5 on the axis with respect to the optical system base 7.When adjusting the distance along the optical axis of the projectinglens 2 between the image display plane of the image generator 1 and theprojecting lens 2 or the optical system base 7, the relationship inposition and/or attitude (for example, rotational position) between theoptical system base 7 or the projecting lens 2 and the free-form curvedsurface mirror 5 or the axis passing the substantially center of thefree-form curved surface mirror 5 and fixed to the optical system base 7is prevented from being changed by adjusting the distance along theoptical axis of the projecting lens 2 between the image display plane ofthe image generator 1 and the projecting lens 2 or the optical systembase 7. In FIG. 8, a pin 17 as the rotational axis supports the centerof the free-form curved surface mirror 5 at both ends thereof so thatthe free-form curved surface mirror 5 is supported thereon in arotatable manner. A lower end of the free-form curved surface mirror 5is connected to a butterfly fixing nut 19 through a rotary guide groove18. By the butterfly fixing nut 19, the lower end of the free-formcurved surface mirror 5 slides along the rotary guide groove 18 so thatthe free-form curved surface mirror 5 is rotatable on the pin 17.Accordingly, an angle between a normal line at the center of thereflecting surface of the free-form curved surface mirror 5 and theoptical axis of the projecting lens 2, that is, an inclination angle ofthe free-form curved surface mirror 5 is adjusted.

In the embodiment, for the image generator 1, three transmission typeliquid crystal panels 31 corresponding to red, green and blue are used.The images from these liquid crystal panels are combined by across-dichroic prism 32.

The images of red, green and blue can be focused by moving the liquidcrystal panels 31 independent of each other. However, in such case,physical values to be compensated for positioning the projected image,positioning pixels, correcting the aberration on the image plane and soforth are numerous. Therefore, it is difficult for all of theadjustments to be brought about by only moving each of the liquidcrystal panels 31. Accordingly, in the embodiment, the movement of eachof the liquid crystal panels 31 is used for positioning the pixels, theadjusting mechanism 15 for supporting the image generator 1 is used forpositioning the projected image and correcting the aberration on theimage plane to be separated from adjusting each of the liquid crystalpanels 31. Further, a distortive aberration is corrected by the rotationof the free-form curved surface mirror 5. In the embodiment, acorrecting mechanism is divided in accordance with the physical valuesto be corrected so that the focusing of the image can be easily done.

The division of the correcting mechanism as mentioned above can be doneby the following reason. That is, in the embodiment, (1) the front group12 of the projecting lens 2 is used as the main lens for projecting ontothe screen 3 the displayed images on the liquid crystal panels 31 whilethe front group 12 corrects the basic aberration in the rotationallysymmetrical optical system, (2) the rear group 13 of the projecting lens2 is the free-form curved surface lens rotationally asymmetrical tocorrect mainly the aberration on the image plane, and (3) the free-formcurved surface mirror 5 corrects mainly the distortive aberration, sothat the above mentioned correcting mechanism is obtained.

Another embodiment of the projecting optical unit of the invention isshown in FIG. 9. A difference thereof from FIG. 8 is that the lens groupof the maximum positive power (not shown, and hereafter called as apower lens) in the front group of the projecting lens 2 is movableaxially. For moving the power lens axially, the lens holder (lens tube)has an oblique guide groove 36 for guiding the lens so that the innerlens group is rotated along the groove. In FIG. 9, a lens fixingbutterfly nut 37 is connected to the power lens or a holder thereof andis moved along the guide groove 36 to move the power lens along itsaxis. That is, in the embodiment, the mechanism for focusing is formedby the guide groove 36 and lens fixing butterfly nut 37. If theprojecting lens 2 has this additional function, the adjusting mechanism35 fixed to the optical system base 7 in such a manner that the imagegenerator 1 is adjustable may be eliminated. Further, by the adjustingmechanism of the power lens as shown in FIG. 8, at least the adjustmentof the distance in the forward and backward direction (Z axis direction)may be eliminated.

As mentioned above, in the embodiments, the rear projection type colorimage display device is realized, by which the depth size of the set isdecreased and the assembly and adjustment can be easily done. Further, aunit in which the planar reflection surface mirror as included by theabove optical system is eliminated and which includes from the imagedisplay element to the free-form curved surface mirror is a frontprojection display. Therefore, the compact front projection displaydevice with the extremely decreased distance from the device to thescreen is obtainable.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A projection type image display device comprising: an image displayelement; a first optical system including a projecting lens which isarranged to enlarge an image formed on the image display element to beprojected onto a screen, and includes a front group having a coaxialoptical system having a surface symmetrical with respect to an axispassing a center of an image plane of the image display element, and arear group having at least one free-form curved surface lens having afree-form curved surface shape on at least one of side surfaces thereofopposite to each other, a second optical system having at least onefree-form curved surface mirror having a free-form curved surface shapeso that the image enlarged by the projecting lens is projected obliquelyonto a screen, and a mechanism enabling the free-form curved surfacemirror to be rotated on an axis passing a center of the free-form curvedsurface mirror, wherein the image display element, the projecting lensand the second optical system are fixed to a common optical system base.2. A projection type image display device according to claim 1, furthercomprising a mechanism for at least one of adjusting an angle betweenthe optical axis of the projecting lens and a direction of a lightemitted from an image generator including the image display element andadjusting an optical distance between the image generator and theprojecting lens.
 3. A projection type image display device according toclaim 1, further comprising a mechanism enabling a lens subgroup ofmaximum positive power in the front group of the projecting lens to bemoved along the optical axis of the projecting lens.
 4. An optical unitusable for a projection type image display device, comprising: an imagedisplay element; a first optical system including a projecting lenswhich is arranged to enlarge an image formed on the image displayelement to be projected onto a screen, and includes a front group havinga coaxial optical system having a surface symmetrical with respect to anaxis passing a center of an image plane of the image display element,and a rear group having at least one free-form curved surface lenshaving a free-form curved surface shape on at least one of side surfacesthereof opposite to each other, a second optical system having at leastone free-form curved surface mirror having a free-form curved surfaceshape so that the image enlarged by the projecting lens is projectedobliquely onto a screen, and a mechanism enabling the free-form curvedsurface mirror to be rotated on an axis passing a center of thefree-form curved surface mirror, wherein the image display element, theprojecting lens and the second optical system are fixed to a commonoptical system base.
 5. An optical unit according to claim 4, furthercomprising a mechanism for at least one of adjusting an angle betweenthe optical axis of the projecting lens and a direction of a lightemitted from an image generator including the image display element andadjusting an optical distance between the image generator and theprojecting lens.
 6. An optical unit according to claim 4, furthercomprising a mechanism enabling a lens subgroup of maximum positivepower in the front group of the projecting lens to be moved along theoptical axis of the projecting lens.
 7. An optical unit usable for aprojection type image display device, comprising: an image displayelement; a first optical system including a projecting lens which isarranged to enlarge an image formed on the image display element to beprojected onto a screen, and includes a front group having a coaxialoptical system having a surface symmetrical with respect to an axispassing a center of an image plane of the image display element, and arear group having at least one free-form curved surface lens having afree-form curved surface shape on at least one of side surfaces thereofopposite to each other, a second optical system having at least onefree-form curved surface mirror having a free-form curved surface shapeso that the image enlarged by the projecting lens is projected obliquelyonto a screen, and a mechanism for at least one of adjusting an anglebetween the optical axis of the projecting lens and a direction of alight emitted from an image generator including the image displayelement and adjusting an optical distance between the image generatorand the projecting lens, wherein: the image display element, theprojecting lens and the second optical system are fixed to a commonoptical system base, and the mechanism has a guide for guiding the imagedisplay element so that the image display element is movable along theoptical axis of the projecting lens with respect to the first opticalsystem.
 8. An optical unit according to claim 7, wherein the mechanismprevents at least one of rotationally and axially positionalrelationships between the front and rear groups of the projecting lensfrom being changed when the image display element is moved along theguide.
 9. An optical unit according to claim 7, wherein the mechanismprevents at least one of rotationally and axially positionalrelationships between the first and second optical systems from beingchanged when the image display element is moved along the guide.
 10. Anoptical unit according to claim 7, wherein the mechanism prevents arotational positional relationship between the image display element andthe front group from being changed when the image display element ismoved along the guide.
 11. An optical unit according to claim 7, whereinthe mechanism has a fixing member for preventing an axial positionalrelationship between the image display element and the first opticalsystem from being changed after the axial positional relationshipbetween the image display element and the first optical system isadjusted along the guide.